1. Technical Field of the Invention
This invention relates to radio telecommunication systems and, more particularly, to a system and method of announcing the availability of a called party.
2. Description of Related Art
Whenever an attempt is made to deliver a call to a called party, and there is no answer, there is no page response, the call is aborted, or there is some other reason that the call cannot be delivered, prior systems generated an announcement from the mobile switching center (MSC) serving the called party (the serving system) to the calling party telling him that the call cannot be delivered and, if possible, providing a reason for non-delivery. To do this, prior systems seize a trunk all the way from the serving system to the originating system to deliver this announcement. This can be extremely expensive to the system operator, and ties up valuable network resources. It can be expensive for the subscriber as well, since some cellular operators charge subscribers for long distance announcements from the serving system to the originating system.
An additional problem arises because some cellular operators do not allow internal trunks in the Public Land Mobile Network (PLMN) to be utilized for such announcements. Instead, Public Switched Telephone Network (PSTN) trunks, which are very expensive and often congested, must be utilized in that instance. Oftentimes, a calling party is kept waiting up to 20 seconds or more, and then receives a congestion signal.
When several callers from several originating systems try to call the subscriber in the serving system at or near the same time, and the calls cannot be delivered, then multiple trunks must be seized in order to carry announcements from the serving system to the multiple originating systems. In addition, an announcement machine is required in the serving system for each announcement. Thus, when multiple announcements must be made at the same time, multiple announcement machines are required. However, many operators cannot afford to purchase and operate a large number of announcement machines. Therefore, they may purchase only a few machines. The announcement machines are used to send all kinds of announcements, therefore, there may be an insufficient number of machines to send announcements to all calling parties. In that case, some of the calling parties receive only a congestion signal, with no explanation.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein.
In order to overcome the disadvantage of prior systems which make announcements to the calling party from the serving system, it would be advantageous to have a system and method which announces the availability of a called party from the originating system. In an alternative embodiment, the announcement may be made from the serving system if the originating system's announcement machines are congested. Such a system provides for better usage of trunk circuits between originating and serving MSCs; better call treatment (i.e., fewer congestion tones after call setup); reduced announcement machine congestion; and reduced costs to the operator due to non-billable calls, since the trunk between the serving system and the originating system is preferably not utilized to deliver the announcement. The present invention provides such a system and method.